80 lines
2.2 KiB
C++
80 lines
2.2 KiB
C++
/*
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* Copyright 2021 Google LLC
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* https://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include "sampler.h"
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#include <cmath>
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#include <cstdint>
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#include <vector>
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#include "random_generator.h"
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namespace dist_proc {
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namespace aggregation {
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namespace internal {
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void KllSampler::Reset() {
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sampled_item_ = 0;
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item_weight_ = 0;
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capacity_ = 2;
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num_replaced_levels_ = 1;
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}
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void KllSampler::Add(const int64_t item) {
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if (compactor_stack_->random()->UnbiasedUniform(++item_weight_) == 0) {
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sampled_item_ = item;
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}
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if (item_weight_ >= capacity_) {
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AddSampleToCompactorStackAndRestart();
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}
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}
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void KllSampler::AddWithWeight(int64_t item, int weight) {
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if (weight > 0) {
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if (item_weight_ + weight < capacity_) {
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item_weight_ += weight;
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if (compactor_stack_->random()->UnbiasedUniform(item_weight_) <
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static_cast<uint64_t>(weight)) {
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sampled_item_ = item;
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}
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} else {
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int64_t added_weight = capacity_ - item_weight_;
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if (compactor_stack_->random()->UnbiasedUniform(capacity_) <
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static_cast<uint64_t>(added_weight)) {
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sampled_item_ = item;
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}
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item_weight_ = capacity_;
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AddSampleToCompactorStackAndRestart();
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AddWithWeight(item, weight - added_weight);
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}
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}
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}
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void KllSampler::DoubleCapacity() {
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capacity_ *= 2;
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num_replaced_levels_++;
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}
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void KllSampler::AddSampleToCompactorStackAndRestart() {
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compactor_stack_->AddWithWeight(sampled_item_, item_weight_);
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item_weight_ = 0;
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sampled_item_ = 0;
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}
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} // namespace internal
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} // namespace aggregation
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} // namespace dist_proc
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